1. Field of the Invention
The present invention generally relates to an embroidery data processing apparatus, and particularly to such an apparatus which processes embroidery data utilized by a sewing machine for embroidering a plurality of areas by filling the areas with stitches.
2. Related Art Statement
There is known a sewing machine which automatically embroiders an area defined by a plurality of points, by filling the area with stitches. The sewing machine embroiders the area by automatically displacing a work fabric on which the embroidery is formed, relative to a needle which is reciprocated vertically to form the stitches filling the area. The sewing machine is operated according to sets of stitch position data representative of stitch positions at which the sewing machine sticks the needle in the work fabric. Each set of stitch position data consists of the coordinate values of a corresponding stitch position in a coordinate system provided for a virtual plane parallel to the work fabric. There is also known an apparatus for processing embroidery data utilized by such a sewing machine for automatically embroidering an area. The embroidery data processed by the apparatus may be stitch position data as indicated above or, alternatively, stitch position-related data different from the stitch position data. The stitch position-related data is, for example, a combination of sets of position data representative of the points defining the area, and a set of stitch density data indicative of a density of stitches, i.e., number of stitches formed in unit area. While the sewing machine produces stitch position data by utilizing such stitch position-related data, it embroiders the area.
For embroidering an area, a start and an end position of the embroidering are specified. While it had conventionally been carried out by an operator to specify the embroidery start and end positions of an area, U.S. patent application Ser. No. 539,207 filed on Jun. 18, 1990, the assignee of which is the assignee of the present application, proposes an embroidery data processing apparatus which automatically specifies the embroidery start and end positions of an area. The apparatus specifies positions or points one by one on the outline of the area in one of clockwise or counterclockwise directions so that the specified points cooperate with each other to define the area or the outline thereof, and determines the first and last specified points of the defining points as the embroidery start and end positions of the area.
The above indicated apparatus determines the embroidery start and end positions of an area according to simple control program. However, in the case where two or more areas are embroidered in succession, the apparatus may specify inappropriate embroidery start and/or end positions for the areas. In order to embroider, for example, two successive areas with a continuous thread, the formation of a transfer stitch from the embroidery end position of the first (prior) one of the two successive areas to the embroidery start position of the second (subsequent) area is needed. Depending upon the embroidery end and start positions specified for the respective two successive areas, the length of the transfer stitch may adversely be increased. As the length of a transfer stitch is increased, a longer time is required for embroidering the areas. In addition, an unnecessary length of thread is consumed. Furthermore, if the transfer stitch passes outside the areas, the external appearance of the embroidery of the areas is deteriorated.
It is considered to automatically determine the most distant, or substantially the most distant, two of the points defining an area to be embroidered, as the embroidery start and end positions of the area. This manner is also subject to the above indicated problems.